Poor Lady Gaga, did you see that she was hospitalized on Wednesday for altitude sickness? No, she wasn't climbing Everest, but she was performing in Denver, where the low oxygen levels in the Mile-High City can trigger acute mountain sickness -- which can result in headache, vomiting, weakness, dizziness, fatigue, and difficulty sleeping.

Dealing with what sounds like the worst hangover in the world was no reason she couldn't take a good selfie, though. Lady Gaga's photo showed her rocking thick black eyeliner, giant sweeping false eyelashes ... and an oxygen mask.

Everyone from Justin Bieber to Lily Allen to Miley Cyrus has been working the camera from their sickbed lately. You'd think they would have better things to do, like oh I don't know, recovering, but here are 6 examples of celebs who are big fans of the hot new hospital selfie trend.

Whose photo is the most ridiculous? Personally, I'm voting for Justin Bieber.